Chewing gum base manufacturing process using plurality of filler feed inlet locations

ABSTRACT

A process for continuously producing a chewing gum base having the steps of continuously adding a hard elastomer, a filler and lubricating agents into a continuous mixer, subjecting the elastomer, filler and lubricating agents to a dispersive mixing operation followed by a distributive mixing operation and continuously discharging the resulting chewing gum base from the mixer while the adding and mixing steps are in progress. The filler is introduced into the continuous mixer at a plurality of spatially separated feed inlets. Preferably part of the filler is introduced into the mixer prior to the dispersive mixing zone, and a portion of the filler is introduced into the mixer downstream of the dispersive mixing zone but prior to the distributive mixing zone.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is the 35 USC 371 national stage application ofPCT/US95/03229, filed Mar. 13, 1995, which is a continuation-in-part ofthe following U.S. patent applications: 1) Ser. No. 08/126,319, filedSep. 24, 1993, now entitled "Continuous Chewing Gum Base ManufacturingProcess Using Highly Distributive Mixing", now U.S. Pat. No. 5,562,936;2) Ser. No. 08/136,589, filed Oct. 14, 1993, now entitled "ContinuousChewing Gum Base Manufacturing Process Using A Mixing RestrictionElement", now U.S. Pat. No. 5,486,366, which is a continuation-in-partof Ser. No. 08/126,319; 3) Ser. No. 08/141,399, filed Oct. 22, 1993,entitled "Continuous Gum Base Manufacturing Using Sequential Mixers",now U.S. Pat. No. 5,397,580; and 4) Ser. No. 08/362,254, filed Dec. 22,1994, entitled "Total Chewing Gum Manufacture Using High EfficiencyContinuous Mixing", now U.S. Pat. No. 5,543,160, which is acontinuation-in-part of Ser. No. 08/305,363, filed Sep. 13, 1994, alsoentitled "Total Chewing Gum Manufacturing Using High EfficiencyContinuous Mixing", now abandoned. The disclosure of each of theforegoing documents is hereby incorporated by reference.

FIELD OF THE INVENTION

This invention is directed to a continuous process for the manufactureof chewing gum bases.

BACKGROUND OF THE INVENTION

A typical chewing gum base includes one or more elastomers, one or morefillers, one or more elastomer solvents, softening agents and optionalplastic polymers and miscellaneous colors, flavors and antioxidants. Dueprimarily to the difficulty in melting and dispersing the elastomershomogeneously among the other gum base ingredients, gum base manufacturehas typically been a tedious and time-consuming batch process. Forexample, one such conventional process uses a sigma blade batch mixerhaving a front to rear blade speed ratio of 2:1, and a mixingtemperature of about 80-125° C.

In this conventional process, initial portions of elastomer, elastomersolvent and filler are added to the heated sigma blade mixer and blendeduntil the elastomer is melted or smeared and thoroughly mixed with theelastomer solvent and fillers. Then the remaining portions of elastomer,elastomer solvent, softening agents, fillers and other ingredients areadded sequentially, in a stepwise fashion, often with sufficient timefor each stepwise addition to become completely mixed before adding moreingredients. Depending on the composition of the particular chewing gumbases and, in particular, the amount and type of elastomer, considerablepatience may be required to insure that each ingredient becomesthoroughly mixed. Overall, anywhere from one to four hours of mixingtime can be required to make one batch of chewing gum base using aconventional sigma blade mixer.

After mixing, the molten gum base batch must be emptied from the mixerinto coated or lined pans, or pumped to other equipments such as aholding tank or a filtering device, then extruded or cast into shapes,and allowed to cool and solidify, before being ready for use in chewinggum. This additional processing and cooling requires even more time.

Various efforts have been undertaken to try to simplify and reduce thetime required for gum base manufacture. European Patent Publication No.0 273 809, in the name of General Foods France, discloses a process formaking nonadhesive chewing gum base by blending elastomer and fillercomponents together in an industrial mill type mixer to form anonadhesive premix, dividing the premix into fragments, and blending thepremix fragments and at least one other nonadhesive gum base componenttogether in a powder mixer. Alternatively, the premix fragments andother base components can be added to an extruder along with otherchewing gum components to accomplish direct manufacture of chewing gum.

French Patent Publication No. 2 635 441, also in the name of GeneralFoods France, discloses a process for making a gum base concentrateusing a twin screw extruder. The concentrate is prepared by mixing highmolecular weight elastomers and plasticizers in desired proportions andfeeding them into the extruder. Mineral fillers are added to theextruder downstream of the feed inlet of the elastomer/plasticizerblend. The resulting gum base concentrate has a high level ofelastomers. The concentrate can then be mixed with the other gum baseingredients to provide a complete gum base.

U.S. Pat. No. 3,995,064, issued to Ehrgott et al., discloses thecontinuous manufacture of gum base using a sequence of mixers or asingle variable mixer.

U.S. Pat. No. 4,187,320, issued to Koch et al., discloses a two stageprocess for preparing a chewing gum base. In the first stage, a solidelastomer, an elastomer solvent, and an oleaginous plasticizer arecombined and mixed together under high shear. In the second stage, ahydrophobic plasticizer, a non-toxic vinyl polymer, and an emulsifierare added to the mixture and mixed using high shear.

U.S. Pat. No. 4,305,962, issued to Del Angel, discloses anelastomer/resin masterbatch formed by mixing a finely ground ester gumresin with a latex elastomer to form an emulsion, coagulating theemulsion using sodium chloride and sulfuric acid, separating thecoagulated solid crumbs from the liquid phase, washing the solid crumbs,and removing the excess water.

U.S. Pat. No. 4,459,311, issued to DeTora et al., discloses making gumbase using two separate mixers--a high intensity mixer forpre-plasticizing the elastomer in the presence of a filler, followed bya medium intensity mixer for ultimately blending all the gum basecomponents together.

U.S. Pat. No. 4,968,511, issued to D'Amelia et al., discloses thatchewing gum can be made directly in a one-step compounding process(without making an intermediate gum base) if certain vinyl polymers areused as the elastomer portion.

Several publications disclose that a continuous extruder can be used tomake the ultimate chewing gum product after a separate process haspreviously been used to make the chewing gum base. These publicationsinclude U.S. Pat. No. 5,135,760, issued to Degady et al.; U.S. Pat. No.5,045,325, issued to Lesko et al., and U.S. Pat. No. 4,555,407, issuedto Kramer et al.

Notwithstanding the prior efforts described above, there is a need anddesire in the chewing gum industry for a continuous process which caneffectively and efficiently be used to make a variety of completechewing gum bases without limiting the type or quantity of elastomeremployed, and without requiring preblending or other pretreatment of theelastomer.

Continuous gum base manufacturing processes, while desirable, present anumber of difficulties. One of these is that continuous equipment has agiven processing length once set up for operation. This length islimited in practice by what is commercially available, and is often lessthan what may be desired from the gum base manufacture's standpoint. Asa result, continuous mixing operations have less degrees of freedom thantraditional batch processes. For example, in a batch process, if longermixing times are needed, it is a simple matter to continue mixing.However, the residence time in a continuous mixer is a function of theoperating speed and feed rates. Therefore, to change the mixing time,some other factor must be adjusted and accommodated. Further, in a batchprocess, additional ingredients can be added at any time. Commercialcontinuous mixers have a limited number of feed inlets at fixedpositions. Therefore the additional ingredients can be added at onlypreset points in the mixing process.

Also, in a batch mixer, dispersive and distributive mixing can beindependently varied and controlled. On a continuous mixer, changes toone type of mixing will often also affect the other type of mixing. Ifthe amount of the machine used for high shear mixing is increased, thereis less machine available for distributive mixing. Also, if the speed isincreased, heat may be generated beyond the ability of the coolingcapabilities of the equipment.

One of the particular problems that has been encountered duringdevelopment of continuous gum base manufacturing processes is that theproperties of the chewing gum base, particularly the softness of thechew, is a function of the gum base ingredients and the mixingconditions that are applied to those ingredients. However, the mixingconditions are also a function of the gum base ingredients, as well asthe type of mixing elements being used, the temperature and viscosity ofthe ingredients and the fullness of the mixer barrel. For example, ifthere is a high content of filler in the base, more aggressive mixingoccurs in the mixer because the filler acts as an abrasive. Conversely,if the filler level in the gum base is low, the mixing is lessaggressive, and may not produce sufficient dispersive mixing of theelastomer.

SUMMARY OF THE INVENTION

It has been discovered that one way to control the mixing process,particularly during dispersive mixing where hard elastomers aremasticated, yet at the same time provide all of the ingredients desiredin the chewing gum base, is to add the filler at a plurality of feedinlet locations in the continuous mixing process.

In one aspect, the invention is a process for continuously producing achewing gum base comprising the steps of continuously adding chewing gumbase ingredients, including a hard elastomer, filler and one or morelubricating agents, into a continuous blade and pin mixer having aplurality of spatially separated feed inlets, at least a portion of thehard elastomer and a portion of the filler being introduced into themixer through one or more first feed inlets and a portion of the fillerbeing introduced into the mixer through one or more second feed inletslocated downstream of the first feed inlets; subjecting the chewing gumbase ingredients to continuous mixing operations within the mixer,thereby producing a chewing gum base; and continuously discharging thechewing gum base from the mixer while chewing gum base ingredientscontinue to be introduced and mixed within.

In a second aspect, the invention is a process for continuouslyproducing a chewing gum base comprising the steps of continuously addingchewing gum base ingredients, including a hard elastomer, filler and oneor more lubricating agents, into a continuous mixer having at least onedispersive mixing zone and at least one distributive mixing zone and aplurality of spatially separated feed inlets, at least a portion of thehard elastomer and a portion of the filler being introduced into themixer through one or more feed inlets located before the end of thedispersive mixing zone and a portion of the filler being introduced intothe mixer through one or more feed inlets located downstream of thedispersive mixing zone and before the end of the distributive mixingzone, the ratio of the amount of filler added before the end of thedispersive mixing zone to the amount of filler added downstream of thedispersive mixing zone being optimized so that the gum base contains adesired amount of filler and the dispersive mixing is effective toproperly masticate the hard elastomer; subjecting the chewing gum baseingredients to continuous mixing operations within the mixer, therebyproducing a chewing gum base; and continuously discharging the chewinggum base from the mixer while chewing gum base ingredients continue tobe introduced and mixed within the mixer.

In a third aspect, the invention is a process for the continuousmanufacture of chewing gum base in which chewing gum base ingredients,including a hard elastomer, filler and one or more lubricating agents,are continuously added into the continuous mixer and mixed therein toproduce a chewing gum base which is continuously discharged from themixer while chewing gum base ingredients continue to be introduced andmixed within the mixer, and in which the continuous mixer has at leastone dispersive mixing zone, at least one distributive mixing zonedownstream of the dispersive mixing zone and a plurality of spatiallyseparated feed inlets, the method comprising the steps of adding atleast a portion of the hard elastomer, at least a portion of thelubricating agents and a portion of the filler through one or more feedinlets located before the end of the dispersive mixing zone; adding aportion of the filler through one or more feed inlets downstream of thedispersive mixing zone and before the end of the distributive mixingzone; and optimizing the ratio of the amount of filler added in each ofthose locations so that the gum base produced contains a desired amountof filler and the mixing process results in an optimized texture of thegum base.

In a fourth aspect, the invention is a process for continuouslyproducing a chewing gum base comprising the steps of continuously addingchewing gum base ingredients, including a hard elastomer, filler and oneor more lubricating agents, into a continuous mixer comprising aplurality of spatially separated feed inlets, the filler being added ata plurality of the feed inlets; controlling the temperature of the mixerso that, at steady state, the peak temperature is over 250° F.;subjecting the chewing gum base ingredients to continuous mixingoperations within the mixer, thereby producing a chewing gum base; andcontinuously discharging the chewing gum base from the mixer whilechewing gum base ingredients continue to be introduced and mixed withinthe mixer.

The invention has numerous advantages. First, chewing gum base isproduced in a continuous process. If desired, the output can be used tosupply a continuous chewing gum production line or, if sufficient mixingcan be accomplished in the first part of the mixer, the complete chewinggum can be produced in one mixer. Second, the average residence time forgum base ingredients is reduced from hours to minutes. Third, all of thenecessary addition and gum base compounding steps can be performed insequence, preferably using a single continuous mixing apparatus. Fourth,the preferred embodiment provides improved metering and mixing ofintermediate and low viscosity gum base ingredients by adding theseingredients in the liquid state under pressure. Fifth, the invention iseffective for a wide range of gum base compositions, including differentgum base elastomers and elastomer percentages, without requiringpreblending or other pretreatment of the elastomers. Sixth, the gum basecan be produced on demand, eliminating finished base inventory. Thisallows maximum flexibility to react to market demands and formulachanges. Seventh, high quality gum bases, including those containinghigh levels of fats, oil and/or low melting point waxes, can be made ona continuous basis.

The foregoing and other features and advantages of the invention willbecome further apparent from the following detailed description of thepresently preferred embodiments, read in conjunction with theaccompanying examples and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a schematic representation of a twin screw extruder setup for use in practicing the present invention.

FIG. 2 depicts a set of shearing disks used in the extruder of FIG. 1.

FIG. 3 depicts a set of toothed elements used in the extruder of FIG. 1.

FIG. 4 depicts a set of kneading disks used in the extruder of FIG. 1.

FIG. 5 depicts a plurality of kneading disks, set up in a helicalfashion, to form kneading blocks.

FIGS. 6a-e depict schematic sequential representations of gum baseingredients during the mixing process.

FIG. 7 is a perspective view of a single flat mixing paddle as used inpracticing another embodiment of the invention.

FIG. 8 is a side view of the mixing paddle of FIG. 1.

FIG. 9a is a front view of the mixing paddle of FIG. 7, shown at zerodegrees rotation (referred to as the no. 1 position).

FIG. 9b is a front view of the mixing paddle of FIG. 7, shown at 45degrees counter-clockwise rotation (referred to as the no. 2 position).

FIG. 9c is a front view of the mixing paddle of FIG. 7, shown at 90degrees counter-clockwise rotation (referred to as the no. 3 position).

FIG. 9d is a front view of the mixing paddle of FIG. 1, shown at 135degrees counter-clockwise rotation (referred to as the no. 4 position).

FIG. 10a is a perspective view of a feeding element (not a paddleelement) used in the feed areas of a paddle mixer.

FIG. 10b is a front view of the feed element of FIG. 10a.

FIG. 11a is a perspective view of a forward helical mixing paddle whichcan be used in a paddle mixer.

FIG. 11b is a front view of the forward helical mixing paddle of FIG.11a.

FIG. 11c is based on a top view of the forward helical mixing paddle of11a, showing only the top intersection line 92 superimposed over thebottom intersection line 90, and a reference line 91.

FIG. 12a is a perspective view of a reverse helical mixing paddle whichcan be used in a paddle mixer.

FIG. 12b is a front view of the reverse helical mixing paddle of FIG.12a.

FIG. 12c is based on a top view of the reverse helical mixing paddle ofFIG. 12a, showing only the top intersection line 92 superimposed overthe bottom intersection line 90, and a reference line 91.

FIG. 13 is a perspective view of an overall paddle mixing configurationof a paddle mixer.

FIG. 14 is a schematic illustration of a barrel and feeder arrangementwhich can be used in conjunction with the paddle mixer configurationshown in FIG. 13.

FIG. 15 is a cross-sectional view taken along line 15--15 of FIG. 14,showing the relationship between the rotating paddles and the barrelwall.

FIG. 16 is a schematic illustration of two paddle mixers arranged inseries.

FIG. 17 is a partial exploded perspective view of a Buss highefficiency, blade-and-pin mixer used to practice another embodiment ofthe invention, illustrating a mixing barrel and mixing screwarrangement.

FIG. 18a is a perspective view of an on-screw element used on theupstream side of a restriction ring assembly in the high efficiencymixer of FIG. 17.

FIG. 18b is a perspective view of an on-screw element used on thedownstream side of the restriction ring assembly in the high efficiencymixer of FIG. 17.

FIG. 18c is a perspective view of a restriction ring assembly used inthe high efficiency mixer of FIG. 17.

FIG. 19 is a perspective view showing the relative positioning of theelements of FIGS. 18a, 18b and 18c in the high efficiency mixer of FIG.17.

FIG. 20 is a perspective view of a low-shear mixing screw element usedin the high efficiency mixer of FIG. 17.

FIG. 21 is a perspective view of a high-shear mixing screw element usedin the high efficiency mixer of FIG. 17.

FIG. 22 is a perspective view of a barrel pin element used in the highefficiency mixer of FIG. 17.

FIG. 23 is a schematic diagram of an arrangement of mixing barrel pinsand ingredient feed ports used with the high efficiency mixer of FIG.17.

FIG. 24 is a schematic diagram of a presently preferred mixing screwconfiguration used with the high efficiency mixer of FIG. 17.

DETAILED DESCRIPTION OF THE DRAWINGS AND PREFERRED EMBODIMENTS OF THEINVENTION

As noted earlier, gum base ingredients play a functional role duringboth mixing of the gum base and in the final chew characteristics of thechewing gum made from the base. During high shear, dispersive mixing,the filler acts to increase the shear. Some of the other gum baseingredients act as lubricating agents, reducing the shear. Mostelastomer solvents, soft elastomers, plastic polymers and softeningagents generally act as lubricating agents in continuous gum basemanufacturing processes. Some lubricating agents such as polyisobutyleneand the elastomer solvents cause the elastomer to disentangle, whileothers are not miscible with the elastomer and act only to lubricate themixing and shearing operations.

To get an optimized shear in a limited amount of mixing space inside ofcontinuous mixers, the amount of filler introduced into the mixer priorto the distributive mixing zone may therefore often be less than theamount of the filler desired in the final gum base. Thus, the methods ofthe present invention introduce the filler at a plurality of feed inletsso that a desired amount of shear can be achieved in a limited portionof the mixer, yet the final gum base can include all of the elastomer,filler and lubricating agents desired from a sensory and coststandpoint. Preferably, the lubricating agent added before thedispersive mixing will be one that acts as a solvent for the hardelastomer.

In one embodiment of the invention, it is preferable if the dispersivemixing can be accomplished in the first 40% of the barrel length of acontinuous mixer. Therefore, in one embodiment of the invention, thefirst portion of filler will be introduced within the first 40% of thebarrel length, and the second portion is added in the last 60% of thebarrel length.

The invention also contemplates a method of optimizing the process formaking chewing gum base in a continuous process by adjusting the ratioof filler being introduced at the different feed inlets until the propermixing is achieved. For instance, in one set of experiments, the samegum base ingredients can be added at the same places in the mixer foreach run, except that the filler is split at various ratios as it isadded at two different points to the mixer. The desired ratio that willresult in optimum processing, and the range of ratios that will beexperimented with, will of course depend on the gum base formulation,the type of mixer being used, and the arrangement of mixing elements inthe mixer.

The chewing gum base made by the process of the present invention willbe the same as bases made by conventional processes, and can thereafterbe made into conventional chewing gums, including bubble gum, byconventional methods. The methods of production are well known andtherefore not repeated here. Of course, specialized chewing gum, such asnonadhesive chewing gum and bubble gum, will use specialized gum baseingredients. However, those gum base ingredients can be combined usingthe processes herein described.

In general, a chewing gum composition typically comprises awater-soluble bulk portion, a water-insoluble chewable gum base portionand typically water-insoluble flavoring agents. The water-solubleportion dissipates with a portion of the flavoring agent over a periodof time during chewing. The gum base portion is retained in the mouththroughout the chew.

The insoluble gum base generally comprises elastomers, elastomersolvents, softening agents and inorganic fillers. Plastic polymers, suchas polyvinyl acetate, which behave somewhat as plasticizers, are alsooften included. Other plastic polymers that may be used includepolyvinyl laurate, polyvinyl alcohol and polyvinyl pyrrolidone.

Elastomers may constitute about 5 to about 95 percent by weight of thegum base, preferably between 10 and 70 percent by weight and mostpreferably between 15 and 45 percent by weight. Elastomers may includepolyisobutylene, butyl rubber (isobutylene-isoprene copolymer), styrenebutadiene rubber, polyisoprene and butadiene rubber, as well as naturalrubbers such as smoked or liquid latex and guayule, as well as naturalgums such as jelutong, lechi caspi, perillo, massaranduba balata,massaranduba chocolate, nispero, rosindinha, chicle, gutta hang kang ormixtures thereof.

Elastomer used in chewing gum base can generally be categorized as hardelastomers or soft elastomers. Hard elastomers, which are most commonlybutyl rubber and styrene butadiene rubber, generally have a highmolecular weight, typically a Flory molecular weight over 200,000. Atypical butyl rubber used in chewing gum base has a Flory molecularweight of about 400,000. Hard elastomers are those which require highshear, dispersive mixing to be utilized in chewing gum base. Hardelastomers generally do not flow at room temperature, even over anextended period of time, and are not pumpable even when heated totemperatures just below which substantial degradation occurs.

Soft elastomers have a lower molecular weight, typically a Florymolecular weight under 100,000. Polyisobutylene and polybutadiene aretypically soft elastomers. A typical polyisobutylene used in chewing gumbase has a Flory molecular weight of about 53,000. Soft elastomers aregenerally pumpable at temperatures normally used to make chewing gumbase, and will flow at room temperature, though often very slowly.

In addition to Flory molecular weight, sometimes a Stodinger molecularweight is specified. Stodinger molecular weights are generally 1/3 to1/5 of Flory molecular weights. For example, the polyisobutylene havinga Flory molecular weight of 53,000 has a Stodinger molecular weight ofabout 12,000. Sometimes number average or weight average molecularweights are reported, or the measurement method is not reported. In suchinstances, the above recitation of the functionality of the elastomerand how they are mixed in producing the chewing gum base can generallybe used to classify the elastomer as hard or soft.

Elastomer solvents may constitute from about 0 to about 75 percent byweight of the gum base, preferably 5 to 45 percent by weight and mostpreferably 10 to 30 percent by weight. Elastomer solvents includenatural rosin esters such as glycerol ester of wood rosin, glycerolester of partially hydrogenated rosin, glycerol ester of polymerizedrosin, glycerol ester of partially dimerized rosin, glycerol ester ofrosin, pentaerythritol esters of partially hydrogenated rosin, methyland partially hydrogenated methyl esters of rosin, pentaerythritol esterof rosin, resin ester of glycerol abietate or mixtures thereof.Elastomer solvents also include synthetics such as terpene resinsderived from alpha-pinene, beta-pinene and/or d-limonene.

Softening agents include oils, fats, waxes and emulsifiers. Oils andfats, sometimes referred to as plasticizers, include tallow, lard,hydrogenated and partially hydrogenated vegetable oils, such as soybeanoil, cotton seed oil, palm oil, palm kernel oil, coconut oil, sunfloweroil and corn oil, cocoa butter, and lipids made from triglycerides offatty acids. Commonly employed waxes include polywax, paraffin,microcrystalline and natural waxes such as candelilla, beeswax andcarnauba. Paraffin waxes may be considered to be plasticizers.Microcrystalline waxes, especially those with a high degree ofcrystallinity, may be considered as bodying agents or texturalmodifiers.

Emulsifiers, which also sometimes have plasticizing properties, includeglycerol monostearate, lecithin, mono and diglycerides of fatty acids,glycerol mono and distearate, triacetin, acetylated monoglyceride, andglycerol triacetate.

The gum base typically also includes a filler component. The fillercomponent may be calcium carbonate, magnesium carbonate, talc, dicalciumphosphate or the like. The filler may constitute between about 5 andabout 60 percent by weight of the gum base. Preferably, the fillercomprises about 5 to about 50 percent by weight of the gum base.

Further, gum bases may also contain optional ingredients such asantioxidants, colors and flavors.

The temperature attained in the mixer often varies over the length ofthe mixer. The peak temperature in the dispersive mixing zone where highshear mixing elements are located, will preferably be over 175° F., morepreferably over 250° F. and most preferably over 300° F., and even 350°F. for some gum base manufacturing processes.

The insoluble gum base may constitute between about 5 to about 80percent by weight of the gum. More typically the insoluble gum basecomprises between 10 and 50 percent by weight of the gum and most oftenabout 20 to about 35 percent by weight of the gum.

The water soluble portion of the chewing gum may include softeners, bulksweeteners, high intensity sweeteners, flavoring agents and combinationsthereof. Softeners are added to the chewing gum in order to optimize thechewability and mouth feel of the gum. The softeners, which are alsoknown as plasticizers or plasticizing agents, generally constitutebetween about 0.5-15% by weight of the chewing gum. The softeners mayinclude glycerin, lecithin, and combinations thereof. Aqueous sweetenersolutions such as those containing sorbitol, hydrogenated starchhydrolysates, corn syrup and combinations thereof, may also be used assofteners and binding agents in chewing gum.

Bulk sweeteners constitute between 5-95% by weight of the chewing gum,more typically 20-80% by weight of the chewing gum and most commonly30-60% by weight of the chewing gum. Bulk sweeteners may include bothsugar and sugarless sweeteners and components. Sugar sweeteners mayinclude saccharide containing components including but not limited tosucrose, dextrose, maltose, dextrin, dried invert sugar, fructose,levulose, galactose, corn syrup solids, and the like, alone or incombination. Sugarless sweeteners include components with sweeteningcharacteristics but are devoid of the commonly known sugars. Sugarlesssweeteners include but are not limited to sugar alcohols such assorbitol, mannitol, xylitol, hydrogenated starch hydrolysates, maltitol,and the like, alone or in combination.

High intensity sweeteners may also be present and are commonly used withsugarless sweeteners. When used, high intensity sweeteners typicallyconstitute between 0.001-5% by weight of the chewing gum, preferablybetween 0.01-1% by weight of the chewing gum. Typically, high intensitysweeteners are at least 20 times sweeter than sucrose. These may includebut are not limited to sucralose, aspartame, salts of acesulfame,alitame, saccharin and its salts, cyclamic acid and its salts,glycyrrhizin, dihydrochalcones, thaumatin, monellin, and the like, aloneor in combination.

Combinations of sugar and/or sugarless sweeteners may be used in chewinggum. The sweetener may also function in the chewing gum in whole or inpart as a water soluble bulking agent. Additionally, the softener mayprovide additional sweetness such as with aqueous sugar or alditolsolutions.

Flavor should generally be present in the chewing gum in an amountwithin the range of about 0.1-15% by weight of the chewing gum,preferably between about 0.2-5% by weight of the chewing gum, mostpreferably between about 0.5-3% by weight of the chewing gum. Flavoringagents may include essential oils, synthetic flavors or mixtures thereofincluding but not limited to oils derived from plants and fruits such ascitrus oils, fruit essences, peppermint oil, spearmint oil, other mintoils, clove oil, oil of wintergreen, anise and the like. Artificialflavoring agents and components may also be used in the flavoringredient of the invention. Natural and artificial flavoring agents maybe combined in any sensorially acceptable fashion.

Optional ingredients such as colors, emulsifiers, pharmaceutical agentsand additional flavoring agents may also be included in chewing gum.

The preferred process of the present invention may be carried out with avariety of continuous mixing equipment. In some embodiments of theinvention, more than one piece of continuous mixing equipment will becoupled in series. As used in the claims, the term "a continuous mixer"means one mixer or a plurality of mixers in series. Three specific typesof continuous mixing equipment are described in detail below and areshown in the attached drawings: twin screw extruders, paddle mixers andblade-and-pin mixers, which are specialized single screw extruders.Extruders are preferred for use in the present invention, particularlythe blade-and-pin mixer.

A. Twin Screw Extruders

In one embodiment, the invention may be carried out on a twin screwextruder such as depicted schematically in FIG. 1. The twin screwextruder used to practice the preferred embodiment of the invention willbe set up with several different feed inlet locations where chewing gumbase ingredients can be added. The screws inside the barrel of theextruder are equipped with different types of elements along the lengthof the screws. The different mixing zones are sometimes referred to asprocessing zones, and described by the type of elements employed in thezones. The barrel is typically made up of different sections. Thesesections may be heated or cooled independent of other sections. Heatingand cooling is thus typically done by region of the extruder barrel,which generally coincides with the barrel sections. These regions ofheating or cooling may or may not coincide with processing zones,depending on the lengths of the barrel sections and the elements in theprocessing zones.

While different equipment manufacturers make different types ofelements, the most common types of elements include conveying elements,compression elements, reverse conveyance elements, homogenizing elementssuch as shearing disks and toothed elements, and kneading disks andblocks. Conveying elements generally have flights spiraling along theelements with wide gaps between the flights. These elements are used atfeed inlet zones to quickly move material into the body of the extruder.Compression elements have flights with a pitch that narrows as thematerial moves along the flights. This results in compression and highpressure in the forward direction, which is required to force materialdownstream and through the other elements. Reverse conveyance elementshave flights that are angled opposite those of the conveying elements.The flights rotate in a direction that would force material upstream.These elements provide a high back pressure and slow down movement ofthe material through the extruder. Of course, the extruded materialstill works its way opposite the flights to move downstream through thereverse elements. A reverse helical arrangement of kneading blocks canaccomplish a similar result.

Shearing disks, as their name implies, impart high shearing forces onthe material in the extruder, resulting in highly dispersive mixing. Ina twin screw extruder, the shearing disks opposite one another on thetwo different screws have close fitting disk/slot elements, as depictedin FIG. 2. Toothed elements, as depicted in FIG. 3, have gear-like teeththat oppose a cylindrical spacer shaft on the other screw. Toothedelements impart highly distributive mixing. Often the toothed elementsare made in matched sets, with a cylindrical shaft portion and a toothedportion as one unit. Kneading disks, as shown in FIG. 4, have anelliptical shape, and produce a kneading action in the material passingthrough the extruder. Often a plurality of kneading disks will be placednext to each other in a helical arrangement, as shown in FIG. 5,referred to as kneading blocks.

Highly distributive mixing can also be accomplished using reverseconveyance elements that have portions missing from the flights to allowflow counter to the direction of compression. These missing portions maybe arranged as a groove through the flights cut parallel to the lengthof the element. Also, kneading blocks followed by reverse conveyanceelements, to build up high back pressure, also produce highlydistributive mixing.

Mixing-restriction elements produce a high back pressure and some mixingwithout overly restricting throughput. For this reason, nozzles ororifices are not suitable as mixing-restriction elements. As notedabove, reverse conveyance elements provide back pressure, and are thusmixing-restriction elements. Shearing disks, like those shown in FIG. 2,also produce a high back pressure and are thus another example of amixing-restriction element.

The high back pressure is important so that other elements, such asthose that produce highly distributive or highly dispersive mixing, willbe able to function properly. Thus in the preferred embodiment of theinvention, mixing-restriction elements are used after each mixing zone.It is most preferable to use a mixing-restriction element just prior tothe gum base exiting the extruder.

These various types of elements, and other elements useful in twin screwextruders, are well known in the art and are commercially available. Theelements are often specifically designed for the different types ofcommonly available twin screw extruders, which include co-rotation,counter rotation, intermeshing and tangential twin screw extruders.Elements intended for similar functions will vary in design depending onthe type of extruder for which they are intended.

One specific type of element for a specific brand of extruder is anon-intermeshing polygon element sold by the Farrel Corporation, 25 MainStreet, Ansonia, Conn. 06401, for the Farrel-Rockstedt co-rotating twinscrew extruder. It is believed that the non-intermeshing polygonsproduce dispersive mixing.

In preferred embodiments of the invention, the dispersive mixingdisentangles the elastomers with a minimum amount of degradation of thepolymer chains. Thus, while dispersive mixing will inevitably reduce themolecular weight of the polymer, it is preferable to control thedispersive mixing operation to minimize this molecular weight reduction.Preferably, the average molecular weight will not be reduced below theaverage molecular weight of the same polymers mixed into gum base usingconventional processes.

An adequate dispersive mixing will produce a smooth, rubbery fluid, withno detectable lumps of rubber. If only a few lumps of rubber are presentthey may be screened out or dispersed during subsequent mixing steps.However, if the number or size of lumps is excessive, or the processedelastomers and fillers are in the form of an agglomeration or grainymass, the dispersive mixing applied is inadequate.

The distributive mixing should be sufficient to produce a homogeneousgum base, rather than a material that appears to be "sweating", or thathas a marbled or Swiss cheese texture. In the preferred embodiment ofthe invention, the highly distributive mixing is sufficient toincorporate softening agents, particularly fats, oils and waxes, to thesame degree these softening agents are incorporated in conventionalchewing gum base manufacturing processes.

As shown in FIG. 1, for practicing an embodiment of the invention, atwin screw extruder 10 is set up with a first feed inlet location 12adjacent a first processing zone 21 fitted with conveying elements 31,conveying and compression elements 32 and compression elements 35. Thesecond processing zone 23 is equipped with a combination of toothedelements 33, as depicted in FIG. 3, and several sets of shearing disks34, as depicted in FIG. 2. At the end of the second processing zone 23the extruder 10 is equipped with a port 16 which is connected to avacuum source (not shown). The third processing zone 24 containsadditional conveying elements 31, conveying and compression elements 32and compression elements 35. A second feed inlet 13 is provided in theextruder adjacent this second set of conveying elements 31, for feedingadditional gum base ingredients into the third processing zone 24. Feedinlet 13 allows for the addition of powdered ingredients as well asliquid ingredients from pump 41. The fourth processing zone 25 is fittedwith kneading disks 36. At the beginning of the fifth processing zone26, the twin screw extruder 10 has another inlet 15 connected to a pump43 and a feed inlet 14 in the form of a port connected to a side feeder42, which may be a single or twin screw extruder, or even a gear pumpwhich can generate high pressure. The fifth processing zone 26 is fittedwith conveying elements 31, conveying and compression elements 32 andcompression elements 35, which force the gum base ingredients into thesixth and final processing zone 28. Zone 28 contains two sets of toothedelements 33, followed by reverse elements 39 and shearing disks 34.After passing through the shearing disks 34, the gum base ingredientsexit the extruder 10.

It may be preferable to heat some of the ingredients, either to meltthem or to lower their viscosity. As shown in FIG. 1, the extruder 10may be set up with heated tanks 44 and 45, connected respectively topumps 41 and 43, for this purpose. Other commonly used equipment, suchas equipment to monitor the temperature and heat or cool the extruder,is not shown in FIG. 1. The equipment will also include conventionalweighing and feeding devices for continuously adding granulated orpowdered ingredients. All of the ingredients are preferably fed into theextruder by equipment that is controlled to operate at a steady state;although during startup it may be preferable to start feeding someingredients before others, and to feed the ingredients in at differentrates than those desired for steady-state operation.

It will be understood that FIG. 1, as a schematic representation, showsthe various components in their respective order from the standpoint offlow through the extruder 10. Typically the screws are mounted in ahorizontal side-to-side position and feed inlets, especially those opento the atmosphere like the inlet 12 and 13, are placed vertically abovethe screws.

While the arrangement of FIG. 1 is preferred for particular gum bases,other arrangements may be preferred for other gum bases. FIG. 1 depictsan extruder with three general areas of ingredient addition and sixprocessing zones. For some gum bases, two, four or more ingredientfeeding zones may be used, with different numbers of processing zones.FIG. 1 also depicts the use of one set each of long conveying elements31, conveying and compression elements 32 and compression elements 35 inthe first processing zone 21, a short set of conveying and compressionelements 32 in zones 24 and 26, and a short set of conveying elements 31and compression elements 35 in zone 26. In reality, one, two or moreelements of different types and length may be used in these zones. FIG.1 also depicts one set of toothed elements 33 and three sets of shearingdisks 34 in zone 23, but different numbers of these elements, ordifferent elements all together, may be used. Likewise in zones 25 and28, different types of elements that produce distributive mixing may beused, dependent on the gum ingredients being mixed in those zones andthe type of extruder being used.

FIGS. 6a-e represent the state of various gum base ingredients as theyare compounded into chewing gum base. At the beginning, as shown in FIG.6a, the high molecular weight (hard) elastomer 51 and medium molecularweight elastomer 52 are both in the form of granules or particles inwhich the elastomer molecules are tightly bound together. The filler 53is in particulate form, but may not be homogeneously mixed with theelastomers 51 and 52. The elastomer solvent 54 may be present in theform of droplets. As mixing begins, depicted in FIG. 6b, the elastomersolvent 54 becomes associated with the elastomers 51 and 52. With thepresence of the filler 53, elastomer solvent 54 and heat, the granulesbegin to come apart into individual elastomer molecules. Also, thefiller 53 becomes more evenly distributed, and may have its particlesize reduced. As the process continues, the elastomers 51 and 52 becomedisentangled, as shown in FIG. 6c. This disentangling is the result ofsubjecting the elastomers 51 and 52 to highly dispersive mixing.

After this step, the lower viscosity ingredients, such as polyvinylacetate 55, may be added, as shown in FIG. 6d. Initially, this materialwill also be in discrete particles, or droplets as it melts. Furthermixing and further ingredient additions, such as waxes 56 andemulsifiers 57, are subjected to distributive mixing, as depicted inFIG. 6e. Continued highly distributive mixing produces a homogeneouschewing gum base, wherein discrete particles or droplets are notdetectible by sensory perception.

The elastomer may be added at the first feed inlet 12 along withelastomer solvent such as resins and the filler. However, especiallylower weight elastomers may be added at least partially at the secondfeed inlet 13. Portions of the filler may also be added at the secondfeed inlet 13. Polyvinyl acetate may be added via a powder feeder or thesingle screw extruder 42, or a twin screw extruder or gear pump, at thefeed inlet port 14, while melted fats and waxes and oils are added atthe last feed inlet 15. This will result in the filler, elastomer andsome lubricating agents being subjected to highly dispersive mixingfirst before lower viscosity ingredients are added. The toothed elements38, reverse elements 39 and shearing disk 40 after feed inlet 15 resultin highly distributive mixing of all of the low viscosity gum baseingredients with the other gum base ingredients.

A preferred small scale extruder is a model LSM 30.34counter-rotational, intermeshing and tangential twin screw extruder fromLeistritz, Nurenberg, Germany. Other acceptable twin screw extrudersinclude the Japan Steel Works Model TEX30HSS32.5PW-2V intermeshing co-and counter-rotating twin screw extruder, also known as the DavisStandard D-Tex Model, distributed by Crompton & Knowles Corporation, #1Extrusion Dr., Pawcatuck, Conn. 06379, and either the co-rotating orcounter-rotating intermeshing twin screw extruders from Werner &Pfleiderer Corporation, 663 E. Crescent Ave., Ramsey N.J. 07446. It ispreferred to have a long barrel length. A Werner & Pfleidererco-rotational twin screw extruder can go up to a length to diameter(L/D) ratio of 48. The Japan Steel Works Model TEX30HSS32.5PW-2Vextruder may be equipped to have an L/D of 58.

B. Paddle Mixers

Another type of continuous mixer that may be used to practice thepresent invention is a paddle mixer. A mixing paddle 85 having a flat(non-helical) configuration is shown in FIGS. 7-9. The term "mixingpaddle" is defined herein as a four-sided mixing element having two flatsurfaces 86 and 87, and two concave surfaces 88 and 89. The flatsurfaces are parallel to each other and intersect only the concavesurfaces. The concave surfaces oppose each other and intersect eachother at two lines 90 and 91. A non-circular (preferably square) opening94 passes through the center of each mixing paddle 85, in a directionperpendicular to the flat surfaces 86 and 87, and intersects both flatsurfaces. The openings 94 are used for mounting a plurality of paddleson rotating shafts, in a predetermined sequence (FIG. 13).

Referring to FIGS. 9a-d, the mixing paddles 85 can be positioned on ashaft at the same or different rotational angles relative to each other.For purposes of the following description, the "No. 1 position", isdefined pursuant to FIG. 9a, wherein a straight line drawn on the flatsurface 87 and intersecting the lines 90 and 92 coincides with areference line (for example, a vertical line). The "No. 2 position" isdefined pursuant to FIG. 9b, wherein a straight line drawn on the flatsurface 87 and intersecting the lines 90 and 92 is 45 degreescounter-clockwise from the reference line. The "No. 3 position" isdefined pursuant to FIG. 9c, wherein a straight line drawn on the flatsurface 87 and intersecting the lines 90 and 92 is 90 degreescounter-clockwise from the reference line. The "No. 4 position" isdefined pursuant to FIG. 9d, wherein a straight line drawn on the flatsurface 87 and intersecting the lines 90 and 92 is 135 degreescounter-clockwise from the reference line.

Because the paddles 85 in FIGS. 9a-d are symmetrical, there is no needto further define the relative rotational positions of the paddles forangles of 180, 225, 270 and 315 degrees from the reference line. Forexample, a paddle having a rotational position of 180 degrees coincidesexactly with a paddle having a rotational angle of zero (FIG. 9a).Similarly, a paddle having a rotational angle of 225 degrees coincidesexactly with a paddle having a rotation angle of 45 degrees (FIG. 9b); apaddle having a rotational angle of 270 degrees coincides exactly with apaddle having a rotational angle of 90 degrees (FIG. 9c), and a paddlehaving a rotational angle of 315 degrees coincides exactly with a paddlehaving a rotational angle of 135 degrees (FIG. 9d).

It is also understood that each mixing paddle 85 will be in constantrotation during operation of the paddle mixer, due to the rotation ofthe shafts supporting the paddles (FIG. 13). For purposes of describingthe mixing paddles in terms of relative rotational positions (i.e.relative to each other) as explained above, the reference line should bedeemed to rotate as the paddles rotate. For example, if the mixingpaddles shown in FIGS. 9a-d are positioned sequentially on a singleshaft, and if the shaft is rotated 90 degrees, then the chosen referenceline, initially vertical, would rotate to a horizontal position. Inother words, the relative rotational positions of the mixing paddles inFIGS. 9a-d, defined respectively as 1-2-3-4, will not change duringoperation of the paddle mixer.

Referring to FIGS. 10a and 10b, the method of the invention alsoprovides for the use of a minor portion of non-paddle elements known asforward conveying or feed elements 50. Each feed element 50 has a flatfront surface 48, a flat back surface 49 parallel to the front surface,and a non-circular (preferably square) opening 46 perpendicular to andintersecting the front and back surfaces. However, unlike the mixingpaddles described above, the feed elements do not have two concavesurfaces intersecting at two lines. Instead, each feed element 50includes portions of two alternating helical channels 47 and 59. Thehelical channels are more apparent in FIG. 13 wherein a plurality offeed elements 50 are combined in sequence on the rotating shafts 110 toform feed zones in the mixer. The primary purpose of the feed elements50 is to convey chewing gum base ingredients forward to the regions ofthe mixer where paddle mixing takes place.

Referring to FIGS. 11a and 11b, a type of mixing paddle known as aforward helical paddle 95 can also be used with the method of theinvention. When used, the forward helical paddle 95 imparts a slightforward conveying action while mixing the gum base ingredients. Like theflat mixing paddles 85, each forward helical paddle 95 has two flatsurfaces and two concave surfaces 88 and 89. The flat surfaces areparallel to each other and intersect only the concave surfaces. Theconcave surfaces oppose each other and intersect at two lines 90 and 92.Again, a non-circular (preferably square) opening 94 passes through thecenter of each mixing paddle 95 and intersects both flat surfaces.

The difference between the forward helical paddle 95 and the flat mixingpaddle 85 is that, in the flat mixing paddle 85, the lines 90 and 92(defining the intersections of concave surfaces 88 and 89) are parallelto each other as shown in FIG. 8. In the forward helical paddle, theline 90 has been rotated counter-clockwise with respect to the line 92so that the lines are no longer parallel, as shown in FIG. 11b.Similarly, the line 92 has been rotated clockwise with respect to theline 90. The effect of this rotation is to bend the concave surfaces 88and 89 so that these surfaces have a mildly helical configuration.

Referring to FIGS. 12a and 12b, a type of mixing paddle known as areverse helical paddle 96 can also be used with the method of theinvention. When used, the reverse helical paddle 96 imparts a slightresistance to forward conveying of the gum base ingredients while mixingthe ingredients. This causes a locally higher degree of mixer fill andslight elevation in pressure, in the vicinity of the reverse helicalpaddle 96.

The reverse helical paddle 96 is configured in the same Fashion as theforward helical pattern 95 discussed above, except that the lines 90 and92 (defining the intersections of concave surfaces 88 and 89) arerotated in the opposite directions. Referring to FIG. 12a, the line 90has been rotated clockwise with respect to the line 92, and the line 92has been rotated counter-clockwise with respect to the line 90. Theeffect of this rotation is to bend the concave surfaces 88 and 89 sothat these surfaces have a mild reverse helical configuration.

The degree of rotation of lines 90 and 92 for the forward and reversehelical paddles 95 and 96 can be explained with reference to FIGS. 11cand 12c. In FIGS. 11c and 12c, the helical paddles have been viewed fromabove and only the lines 90 and 92 of the paddles are shown,superimposed one on top of the other. A reference line 91 is also shown,indicating the positions of lines 90 and 92 if there were no rotation,as in a flat paddle 85.

Referring to FIG. 11c, the angle "a" is the amount of counter-clockwiserotation of line 90 present in a forward helical paddle 95. The angle"a" should be between about 5 and about 30 degrees, preferably betweenabout 10 and about 18 degrees, most preferably about 13 degrees, 53minutes, 50 seconds. The angle "b" is the amount of clockwise rotationof line 92 present in a forward helical paddle 95. The angle "b" shouldbe between about 5 and about 30 degrees, preferably between about 10 andabout 18 degrees, most preferably about 13 degrees, 53 minutes, 50seconds.

Referring to FIG. 12c, the angle "a" is the amount of clockwise rotationof line 90 present in a reverse helical paddle 96. The angle "a" shouldbe between about 5 and about 30 degrees, preferably between about 10 andabout 18 degrees, most preferably about 13 degrees, 53 minutes, 50seconds. The angle "b" is the amount of counter-clockwise rotation ofline 92 present in a reverse helical paddle 96. The angle "b") should bebetween about 5 and about 30 degrees, preferably between about 10 andabout 18 degrees, most preferably about 13 degrees, 53 minutes, 50seconds.

Referring to FIG. 13, the mixing paddles and feed elements are assembledon two parallel shafts 110 in a predetermined configuration. In theembodiment shown, for a 5-inch paddle mixer, each of the shafts 110 hasan active length of 36 inches and a square cross-sectional area of 1.375inches×1.375 inches (1.891 square inches). The parallel shafts 110 arespaced apart at a distance of 3.5 inches (center to center). The shafts110 are adapted for co-rotation (rotation in the same direction) insidea mixing barrel. Each of the shafts 110 supports an identicalarrangement of mixing paddles and feed elements. The mixing paddles andfeed elements on the adjacent shafts may intermesh, as shown in FIG. 13,but do not touch each other, as the shafts rotate.

Each of the shafts 110 is long enough to accommodate thirty-six inchesof elements, each having a length of 1 inch, a maximum diameter of 4.874inches and a minimum diameter of 2 inches. Two or more 1-inch segmentsmay be combined to make longer elements without affecting the operation.For instance, the feed elements 50 often have a length of 2 inches. Forpurposes of the invention, a large portion of each shaft should becovered with mixing paddles. Generally, at least about 40 percent ofeach shaft should be covered with mixing paddles. Preferably at leastabout 50 percent of each shaft is covered with mixing paddles, mostpreferably at least about 60 percent. Of the mixing paddles, a majorityshould be flat mixing paddles as opposed to forward helical or reversehelical paddles. In the embodiment shown in FIG. 13, 67 percent of theshaft length is covered with mixing paddles (24 one-inch elements) and33 percent of the shaft length is covered with feed elements (6 two-inchelements).

The mixer configuration 102 in FIG. 13 includes two feed zones 125 and135, and two paddle mixing zones 130 and 150. The specific mixerconfiguration is indicated in Table 1 below. In Table 1 and othertables, the following abbreviations are used:

FC--feed conveying element (each occupying two 1-inch positions)

FP--flat mixing paddle (each occupying one 1-inch position)

FH--forward helical mixing paddle (each occupying one 1-inch position)

RH--reverse helical mixing paddle (each occupying one 1-inch position)

                  TABLE 1                                                         ______________________________________                                        Mixer Configuration (Per Shaft) - FIG. 13                                     Longitudinal    Rotational                                                                             Longitudinal  Rotational                             Position                                                                              Element Position Position                                                                              Element                                                                             Position                               ______________________________________                                         1      FC      4        19      FP    3                                       2      FC      4        20      FC    3                                       3      FC      4        21      FC    3                                       4      FC      4        22      FC    3                                       5      FC      4        23      FC    3                                       6      FC      4        24      FP    3                                       7      FC      4        25      FP    3                                       8      FC      4        26      FP    3                                       9      FP      4        27      FP    1                                      10      FP      4        28      FP    1                                      11      FP      4        29      FP    1                                      12      FP      2        30      FP    3                                      13      FP      2        31      FP    3                                      14      FP      2        32      FP    3                                      15      FP      3        33      FP    4                                      16      FP      4        34      FP    1                                      17      FP      1        35      FP    2                                      18      FP      2        36      RH    1                                      ______________________________________                                    

The use of two or more feed zones and two or more mixing zones in themixer configuration 102, permits sequential addition and mixing ofdifferent gum base ingredients. For example, a high viscosity portionincluding elastomer, filler, and some resin or polyvinyl acetate can becontinuously fed to the first feed zone 125 in FIG. 13. Theseingredients can then be thoroughly mixed in the first paddle mixing zone130 before being combined with additional ingredients. A lower viscosityportion including waxes (when used), fats, oils, colorants andadditional resin or polyvinyl acetate can be continuously fed to thesecond feed zone 135. All gum base ingredients can then be thoroughlymixed in the second paddle mixing zone 150.

The mixer configuration 102 shown in FIG. 13 is, in practice, surroundedby one or more barrel segments extending the length of the mixerconfiguration 102. FIG. 14 illustrates, schematically, a typical barrel105 surrounding the mixer configuration 102. A motor 101 drives theshafts 110 which support the mixer elements. The gum base ingredientsare fed through feed ports 103 and 123 in the barrel 105. The gum baseremains in the mixer for a sufficient time to ensure homogeneity, forexample, a time on the order of about 20-30 minutes, and exits throughan exit nozzle 155. The barrel 105 may be heated or cooled. Heating maybe accomplished using hot water or a steam jacket surrounding the barrel(not shown). Cooling may be accomplished by supplying cooling water to ajacket surrounding the barrel 105. Alternative methods of heating andcooling may also be employed. Generally, heating is applied at the startup, but cooling is applied in the latter stages to prevent overheatingand base degradation.

The heating and cooling of the barrel should be supplied, as necessary,to maintain the product exit temperatures at about 90° C.-150° C.,preferably at about 100-135° C., during mixing of the gum baseingredients.

FIG. 15 is a sectional view of the barrel 105 which indicates how thepaddle mixer is able to operate with longer residence times, compared toa conventional twin screw extruder. As shown in FIG. 15, the barrel wall116 has the shape of two intersecting cylinders, each cylinder having adiameter larger than the largest diameter of the mixing paddle 85contained therein. This barrel configuration resembles that of astandard twin screw extruder. However, unlike the screws of a twin screwextruder, the paddles 85 do not mostly fill the space defined by thebarrel wall 116.

The mixing paddles 85 have a typically close tolerance with the barrelwall 116, and with each other, in the vicinity of the lines 90 and 92where the concave surfaces intersect. For paddles 85 having a longdiameter of 4.874 inches, the closest tolerance between each paddle andthe barrel wall 116 may be on the order of about 0.048 inch to about0.078 inch, and the closest tolerance between the two paddles may be onthe order of about 0.060 inch to about 0.090 inch. However, away fromthe lines 90 and 92, the distance between each paddle 85 and the barrelwall 116 is much greater. Due to the unique design of the paddles 85,the percentage of barrel space occupied by the paddles 85 is muchsmaller than for a conventional twin screw extruder. Also, the pressurein the paddle mixer should remain below about 50 psig, preferably belowabout 20 psig, when there is a large percentage of paddles compared toother elements. Each paddle 85, when viewed from the front as in FIG.15, has a smaller width than height. Preferably, the ratio of height towidth of each mixing paddle is more than 1.5:1. Most preferably, theratio of height to width for each mixing paddle is more than 2:1.

The large amount of available barrel space also allows the method of theinvention to be practiced at high residence times in paddle mixers. Thehigh proportion of mixing paddles, especially flat paddles, alsocontributes to the longer residence times and lower pressure. Theaverage residence time in the paddle mixer should be at least about 10minutes, preferably more than 15 minutes, most preferably more than 20minutes.

The remaining operating parameters, e.g., mixer rpm, feed rates,production rates, etc. vary depending on the size of the mixer and onthe specific gum base composition. A commercially available paddle mixersuitable for practicing the invention is a Teledyne Readco ContinuousProcessor, available from Teledyne Readco in York, Pa. These paddlemixers are available in a wide variety of sizes. Paddle diameters forthe different size mixers range from 2 to 24 inches, and the ratios ofmixer length to diameter (L/D) range from 4:1 to 14:1. For purposes ofthe present invention, the maximum paddle diameter is preferably between2 inches and 5 inches, and the L/D is preferably about 7:1. The paddlemixer configuration and process conditions should be selected so that ahomogeneous gum base product is achieved.

In a particularly useful embodiment, two or more paddle mixers may beused in series, in the manner illustrated in FIG. 16. The use of twomixers in series allows greater flexibility for feeding different gumbase ingredients at different locations. A combination of elastomer,filler and resin can be continuously fed via feed port 103 to the feedbarrel 105 of the first mixer. These materials are mixed in the firstmixer, after which additional resin can be added to the first mixer viafeed port 123. The combined ingredients are blended in the first mixer,and leave the first mixer at the exit 155, whereupon they areimmediately fed into the barrel 205 of the second mixer 208 (powered bymotor 201) via the feed port 203. Polyvinyl acetate can also becontinuously fed to the barrel 205 from hopper 207, via feed conveyor209 and feed port 203.

Further ingredients, such as waxes or oils, can be injected into thesecond mixer from feed tanks 211 and 231, via pumps 213 and 233.Optionally, a portion of ingredients can be added into a downstream feedport 204. After all the components are mixed, the gum base leaves thesecond mixer via exit 255. A wide variety of different feeding andmixing arrangements can also be employed using two or more paddle mixersin series, in order to achieve good dispersion of ingredients and a widevariety of gum base products.

In addition to the paddles described above, a wide variety of mixingpaddles, available from various extruder companies, can be used.Paddles, often called kneading elements, must have the effect of mixingin an extruder. Paddles can be two-sided, three-sided, or multiplesided.

The paddle mixer, which may be referred to as a compounder, hasdifferent characteristics than a typical extruder even though the sameequipment may be used. The difference between an extruder and acompounder is the ratio of paddles or kneading elements to the conveyingelements. Conveying elements and compression elements cause an extruderto build up pressure. Paddles or kneading elements do not build as muchpressure in the extruder, thus there is more mixing with low pressure.If the extruder contains at least 40% kneading elements, then thepressure can be about one-fifth to one-tenth that of a typical extruderwhich uses more conveying and compression elements.

Nearly all extruders can be used as compounders. However, compounderswhich have a low L/D ratio of about 3:1 to 20:1 cannot generally be usedas high pressure extruders. Also, compounders with this low L/D ratiohave less effective shaft length and may require more paddle or kneadingelements compared to conveying elements. For this type of compounder,mixing paddles should cover at least 50%, and preferably at least 60% ofthe shaft. Conversely, for an extruder having an L/D of about 20/1 toabout 40/1, only about 40% of the shaft needs to be covered with mixingpaddles or kneading elements. For extruders with high L/D ratios greaterthan 40/1, only about 30% of the shaft may need to be covered withmixing paddles or kneading elements.

One of the key advantages to the preferred embodiment of the paddlemixer disclosed above is that the residence time is much higher than intypical extruders. Many extruders provide a residence time of less than2 minutes or even less than 1 minute. However, in the preferred paddlemixer described above, a residence time of at least 10 minutes, andpreferably at least 15-20 minutes, can be provided.

C. Blade-and-Pin Mixers

The method of the present invention may also be advantageously performedusing a continuous mixer whose mixing screw is composed primarily ofprecisely arranged mixing elements with only a minor fraction of simpleconveying elements. A presently preferred mixer is a blade-and-pin mixerexemplified in FIG. 17. This mixer may be used to produce not only gumbase, but an entire chewing gum composition. A blade-and-pin mixer usesa combination of selectively configured rotating mixer blades andstationary barrel pins to provide efficient mixing over a relativelyshort distance. A commercially available blade-and-pin mixer is the Busskneader, manufactured by Buss AG in Switzerland, and available from BussAmerica, located in Bloomingdale, Ill.

Referring to FIG. 17, a presently preferred blade-and-pin mixer 100includes a single mixing screw 120 turning inside a barrel 140 which,during use, is generally closed and completely surrounds the mixingscrew 120. The mixing screw 120 includes a generally cylindrical shaft122 and three rows of mixing blades 124 arranged at evenly spacedlocations around the screw shaft 122 (with only two of the rows beingvisible in FIG. 1). The mixing blades 124 protrude radially outward fromthe shaft 122, with each one resembling the blade of an axe.

The mixing barrel 140 includes an inner barrel housing 142 which isgenerally cylindrical when the barrel 140 is closed around the screw 120during operation of the mixer 100. Three rows of stationary pins 144 arearranged at evenly spaced locations around the screw shaft 122, andprotrude radially inward from the barrel housing 142. The pins 144 aregenerally cylindrical in shape, and may have rounded or bevelled ends146.

The mixing screw 120 with blades 124 rotates inside the barrel 140 andis driven by a variable speed motor (not shown). During rotation, themixing screw 120 also moves back and forth in an axial direction,creating a combination of rotational and axial mixing which is highlyefficient. During mixing, the mixing blades 124 continually pass betweenthe stationary pins 144, yet the blades and the pins never touch eachother. Also, the radial edges 126 of the blades 124 never touch thebarrel inner surface 142, and the ends 146 of the pins 144 never touchthe mixing screw shaft 122.

FIGS. 18-22 illustrate various screw elements which can be used toconfigure the mixing screw 120 for optimum use. FIGS. 18a and 18billustrate on-screw elements 60 and 61 which are used in conjunctionwith a restriction ring assembly. The on-screw elements 60 and 61 eachinclude a cylindrical outer surface 62, a plurality of blades 64projecting outward from the surface 62, and an inner opening 66 with akeyway 68 for receiving and engaging a mixing screw shaft (not shown).The second on-screw element 61 is about twice as long as the firston-screw element 60.

FIG. 18c illustrates a restriction ring assembly 70 used to build backpressure at selected locations along the mixing screw 120. Therestriction ring assembly 70 includes two halves 77 and 79 mounted tothe barrel housing 142, which halves engage during use to form a closedring. The restriction ring assembly 70 includes a circular outer rim 72,an inner ring 74 angled as shown, and an opening 76 in the inner ringwhich receives, but does not touch, the on-screw elements 60 and 61mounted to the screw shaft. Mounting openings 75 in the surface 72 ofboth halves of the restriction ring assembly 70 are used to mount thehalves to the barrel housing 142.

FIG. 19 illustrates the relationship between the restriction ringassembly 70 and the on-screw elements 60 and 61 during operation. Whenthe mixing screw 120 is turning inside the barrel 140, and reciprocatingaxially, the clearances between the on-screw elements 60 and 61 and theinner ring 74 provide the primary means of passage of material from oneside of the restriction ring assembly 70 to the other. The on-screwelement 60 on the upstream side of the restriction ring assemblyincludes a modified blade 67 permitting clearance of the inner ring 74.The other on-screw element 61 is placed generally downstream of therestriction ring assembly 70, and has an end blade (not visible) whichmoves close to and wipes the opposite surface of the inner ring 74.

The clearances between outer surfaces 62 of the on-screw elements 60 and61 and the inner ring 74 of the restriction ring assembly 70, which canvary and preferably are on the order of 1-5 mm, determine to a largeextent how much pressure build-up will occur in the upstream region ofthe restriction ring assembly 70 during operation of the mixer 100. Itshould be noted that the upstream on-screw element 60 has an L/D ofabout 1/3, and the downstream on-screw element 61 has an L/D of about2/3, resulting in a total L/D of about 1.0 for the on-screw elements.The restriction ring assembly 70 has a smaller L/D of about 0.45 whichcoincides with the L/D of the on-screw elements 60 and 61, which engageeach other but do not touch the restriction ring assembly.

FIGS. 20 and 21 illustrate the mixing or "kneading" elements whichperform most of the mixing work. The primary difference between thelower shear mixing element 80 of FIG. 20 and the higher shear mixingelement 78 of FIG. 21 is the size of the mixing blades which projectoutward on the mixing elements. In FIG. 21, the higher shear mixingblades 83 which project outward from the surface 81 are larger andthicker than the lower shear mixing blades 84 projecting outward fromthe surface 82 in FIG. 20. For each of the mixing elements 80 and 78,the mixing blades are arranged in three circumferentially-spaced rows,as explained above with respect to FIG. 17. The use of thicker mixingblades 83 in FIG. 21 means that there is less axial distance between theblades and also less clearance between the blades 83 and the stationarypins 144 as the screw 120 rotates and reciprocates axially (FIG. 17).This reduction in clearance causes inherently higher shear in thevicinity of the mixing elements 78. FIG. 22 illustrates a singlestationary pin 144 detached from the barrel 140. The pin 144 includes athreaded base 145 which permits attachment at selected locations alongthe inner barrel shaft 142. It is also possible to configure some of thepins 144 as liquid injection ports by providing them with hollow centeropenings.

FIG. 23 is a schematic view showing the presently preferred barrelconfiguration, including the presently preferred arrangement of barrelpins 144. FIG. 24 is a corresponding schematic view illustrating thepresently preferred mixing screw configuration. The mixer 200 whosepreferred configuration is illustrated in FIGS. 23 and 24 has an overallactive mixing L/D of about 19.

The mixer 200 includes an initial feed zone 210 and five mixing zones220, 230, 240, 250 and 260. The zones 210, 230, 240, 250 and 260 includefive possible large feed ports 212, 232, 242, 252 and 262, respectively,which can be used to add major (e.g. solid) ingredients to the mixer200. The zones 240 and 260 are also configured with five smaller liquidinjection ports 241, 243, 261, 263 and 264 which are used to add liquidingredients. The liquid injection ports 241, 243, 261, 263 and 264include special barrel pins 144 formed with hollow centers, as explainedabove.

Referring to FIG. 23, barrel pins 144 are preferably present in most orall of the available locations, in all three rows as shown.

Referring to FIG. 24, the presently preferred configuration of themixing screw 120 for most chewing gum products is schematicallyillustrated as follows. Zone 210, which is the initial feed zone, isconfigured with about 11/3 L/D of low shear elements, such as theelement 40 shown in FIG. 4. The L/D of the initial feed zone 210 is notcounted as part of the overall active mixing L/D of 19, discussed above,because its purpose is merely to convey ingredients into the mixingzones.

The first mixing zone 220 is configured, from left to right (FIG. 24),with two low shear mixing elements 80 (FIG. 20) followed by two highshear elements 78 (FIG. 21). The two low shear mixing elementscontribute about 11/3 L/D of mixing, and the two high shear mixingelements contribute about 11/3 L/D of mixing. Zone 220 has a totalmixing L/D of about 3.0, including the end part covered by a 57 mmrestriction ring assembly 70 with cooperating on-screw elements 60 and61 (not separately designated in FIG. 24).

The restriction ring assembly 70 with cooperating on-screw elements 60and 61, straddling the end of the first mixing zone 220 and the start ofthe second mixing zone 230, have a combined L/D of about 1.0, part ofwhich is in the second mixing zone 230. Then, zone 230 is configured,from left to right, with three low shear mixing elements 80 and 1.5 highshear mixing elements 78. The three low shear mixing elements contributeabout 2.0 L/D of mixing, and the 1.5 high shear mixing elementscontribute about 1.0 L/D of mixing. Zone 230 has a total mixing L/D ofabout 4.0.

Straddling the end of the second mixing zone 230 and the start of thethird mixing zone 240 is a 60 mm restriction ring assembly 70 withcooperating on-screw elements 60 and 61 having an L/D of about 1.0.Then, zone 240 is configured, from left to right, with 4.5 high shearmixing elements 78 contributing a mixing L/D of about 3.0. Zone 240 alsohas a total mixing L/D of about 4.0.

Straddling the end of the third mixing zone 240 and the start of thefourth mixing zone 250 is another 60 mm restriction ring assembly 70with cooperating on-screw elements having an L/D of about 1.0. Then, theremainder of the fourth mixing zone 250 and the fifth mixing zone 260are configured with eleven low shear mixing elements 80 contributing amixing L/D of about 7%. Zone 250 has a total mixing L/D of about 4.0,and zone 260 has a total mixing L/D of about 4.0.

EXAMPLES 1-3 Continuous Chewing Gum Manufacture

When the chewing gum base is made in a blade-and-pin mixer, it has beenfound that it is possible to complete the making of the chewing gumcomposition in the same mixer. General procedures for making chewing gumbase according to the present invention, and then making that gum baseinto chewing gum, are as follows. In order to accomplish the totalchewing gum manufacture using the preferred blade-and-pin mixer 200(FIG. 17), it is advantageous to maintain the rpm of the mixing screw120 at less than about 150, preferably less than about 100. Also, themixer temperature is preferably optimized so that the gum base is atabout 130° F. or lower when it initially meets the other chewing gumingredients, and the chewing gum product is at about 130° F. or lower(preferably 125° F. or lower) when it exits the mixer. This temperatureoptimization can be accomplished, in part, by selectively heating and/orwater cooling the barrel sections surrounding the mixing zones 220, 230,240, 250 and 260 (FIG. 23).

In order to manufacture the gum base, the following preferred procedurecan be followed. The elastomer, part of the filler, and at least some ofthe elastomer solvent are added to the first large feed port 212 in thefeed zone 210 of the mixer 200, and are subjected to highly dispersivemixing in the first mixing zone 220 while being conveyed in thedirection of the arrow 122. The remaining filler, elastomer solvent (ifany) and polyvinyl acetate are added to the second large feed port 232in the second mixing zone 230, and the ingredients are subjected to amore distributive mixing in the remainder of the mixing zone 230.

Fats, oils, waxes (if used), emulsifiers and, optionally, colors andantioxidants, are added to the liquid injection ports 241 and 243 in thethird mixing zone 240, and the ingredients are subjected to distributivemixing in the mixing zone 240 while being conveyed in the direction ofthe arrow 122. At this point, the gum base manufacture should becomplete, and the gum base should leave the third mixing zone 240 as asubstantially homogeneous, lump-free compound with a uniform color.

The fourth mixing zone 250 is used primarily to cool the gum base,although minor ingredient addition may be accomplished. Then, tomanufacture the final chewing gum product, glycerin, corn syrup, otherbulk sugar sweeteners, high intensity sweeteners, and flavors can beadded to the fifth mixing zone 260, and the ingredients are subjected todistributive mixing. If the gum product is to be sugarless, hydrogenatedstarch hydrolyzate or sorbitol solution can be substituted for the cornsyrup and powdered alditols can be substituted for the sugars.

Preferably, glycerin is added to the first liquid injection port 261 inthe fifth mixing zone 260. Solid ingredients (bulk sweeteners,encapsulated high intensity sweeteners, etc.) are added to the largefeed port 262. Syrups (corn syrup, hydrogenated starch hydrolyzate,sorbitol solution, etc.) are added to the next liquid injection port263, and flavors are added to the final liquid injection port 264.Flavors can alternatively be added at ports 261 and 263 in order to helpplasticize the gum base, thereby reducing the temperature and torque onthe screw. This may permit running of the mixer at higher rpm andthroughput.

The gum ingredients are compounded to a homogeneous mass which isdischarged from the mixer as a continuous stream or "rope". Thecontinuous stream or rope can be deposited onto a moving conveyor andcarried to a forming station, where the gum is shaped into the desiredform such as by pressing it into sheets, scoring, and cutting intosticks. Because the entire gum manufacturing process is integrated intoa single continuous mixer, there is less variation in the product, andthe product is cleaner and more stable due to its simplified mechanicaland thermal histories.

EXAMPLES 1-3

The following Examples 1-3 were run using a Buss kneader with a 100 mmmixer screw diameter, configured in the preferred manner described above(unless indicated otherwise), with five mixing zones, a total mixing L/Dof 19, and an initial conveying L/D of 11/3. The product mixture exitedas a continuous rope.

Liquid ingredients were fed using volumetric pumps into the large feedports and/or smaller liquid injection ports generally positioned asdescribed above, unless otherwise indicated. The pumps wereappropriately sized and adjusted to achieve the desired feed rates.

Dry ingredients were added using gravimetric screw feeders into thelarge addition ports positioned as described above. Again, the feederswere appropriately sized and adjusted to achieve the desired feed rates.

Temperature control was accomplished by circulating fluids throughjackets surrounding each mixing barrel zone and inside the mixing screw.Water cooling was used where temperatures did not exceed 200° F., andoil cooling was used at higher temperatures. Where water cooling wasdesired, tap water (typically at about 57° F.) was used withoutadditional chilling.

Temperatures were recorded for both the fluid and the ingredientmixture. Fluid temperatures were set for each barrel mixing zone(corresponding to zones 220, 230, 240, 250 and 260 in FIGS. 23 and 24),and are reported below as Z1, Z2, Z3, Z4 and Z5, respectively. Fluidtemperatures were also set for the mixing screw 120, and are reportedbelow as S1.

Actual mixture temperatures were recorded near the downstream end ofmixing zones 220, 230, 240 and 250; near the middle of mixing zone 260;and near the end of mixing zone 260. These mixture temperatures arereported below as T1, T2, T3, T4, T5 and T6, respectively. Actualmixture temperatures are influenced by the temperatures of thecirculating fluid, the heat exchange properties of the mixture andsurrounding barrel, and the mechanical heating from the mixing process,and often differ from the set temperatures due to the additionalfactors.

All ingredients were added to the continuous mixer at ambienttemperature (about 77° F.) unless otherwise noted.

EXAMPLE 1 25/75% Split of Filler

This example illustrates the preparation of a gum base to be used tomake a peppermint flavored sugar chewing gum. A blend of 40.854% dustedground isobutylene-isoprene copolymer, 21.176% low molecular weightterpene resin, 21.358% high molecular weight terpene resin, and 16.612%fine ground calcium carbonate was added to the first large feed port 212at 21.3 lb/hr.

A blend of 6.172% high molecular weight polyvinyl acetate, 49.363% lowmolecular weight polyvinyl acetate, 5.790% high molecular weight terpeneresin, 5.790% low molecular weight terpene resin, 31.496% fine groundcalcium carbonate and 1.390% color was added at 20.6 lb/hr. into thesecond large feed port 232. Polyisobutylene (preheated to 250° F.) wasalso added into the second large feed port at 3.5 lb/hr.

A fat mixture (225° F.) was injected into zone 240 at a total rate of14.16 lb/hr. This fat mixture included 37% hydrogenated cottonseed oil,22% hydrogenated soybean oil, 15% partially hydrogenated cottonseed oil,23% glycerol monostearate, 2.4% soy lecithin and 0.12% BHT.

Glycerin was injected into zone 260 at 3.87 lb/hr. A mixture of 85%sucrose and 15% dextrose monohydrate was added into the large feed port262 at 203.1 lb/hr. Corn syrup (100° F.) was injected into zone 260 at30.0 lb/hr. A peppermint flavor was injected into zone 260 at 3.0 lb/hr.

The zone temperatures (Z1-Z5, ° F.) were set at 350, 350, 100, 55 and55, respectively, and the screw temperature (S1) was set at 100° F. Themixture temperatures (T1-T6, ° F.) were measured as 322, 289, 161, 118,109 and 89, respectively. The screw rotation was set at 60 rpm.

The product exited the mixer at 122° F.

EXAMPLE 2 50/50% Split of Filler

This example illustrates the preparation of a gum base to be used tomake a peppermint flavored sugar chewing gum. A blend of 35.089% dustedground isobutylene-isoprene copolymer, 18.188% low molecular weightterpene resin, 18.344% high molecular weight terpene resin, and 28.379%fine ground calcium carbonate was added to the first large feed port 212at 18.8 lb/hr.

A blend of 6.899% high molecular weight polyvinyl acetate, 55.177% lowmolecular weight polyvinyl acetate, 6.472% high molecular weight terpeneresin, 6.472% low molecular weight terpene resin, 23.427% fine groundcalcium carbonate and 1.553% color was added at 22.24 lb/hr. into thesecond large feed port 232. Polyisobutylene (preheated at 250° F.) wasalso added into the second large feed port at 23.0 lb/hr.

A fat mixture (225° F.) was injected into zone 240 at a total rate of14.16 lb./hr. This fat mixture included 37% hydrogenated cottonseed oil,22% hydrogenated soybean oil, 15% partially hydrogenated cottonseed oil,23% glycerol monostearate, 2.4% soy lecithin and 0.12% BHT.

Glycerin was injected into zone 260 at 3.87 lb/hr. A mixture of 85%sucrose and 15% dextrose monohydrate was added into the large feed port262 at 203.1 lb/hr. Corn syrup (100° F.) was injected into zone 260 at30.0 lb/hr. A peppermint flavor was injected into zone 260 at 3.0 lb/hr.

The zone temperatures (Z1-Z5, ° F.) were set at 350, 350, 100, 55, and55, respectively, and the screw temperature (S1) was set at 100° F. Themixture temperatures (T1-T6, ° F.) were measured as 323, 290, 162, 115,107 and 89, respectively. The screw rotation was set at 60 rpm.

The product exited the mixer at 122° F.

EXAMPLE 3 75/25% Split of Filler

This example illustrates the preparation of a gum base to be used tomake a peppermint flavored sugar chewing gum. A blend of 30.708% dustedground isobutylene-isoprene copolymer, 15.917% low molecular weightterpene resin, 16.054% high molecular weight terpene resin, and 37.322%fine ground calcium carbonate was added to the first large feed port 212at 16.3 lb/hr.

A blend of 7.808% high molecular weight polyvinyl acetate, 62.452% lowmolecular weight polyvinyl acetate, 7.325% high molecular weight terpeneresin, 7.325% low molecular weight terpene resin, 13.331% fine groundcalcium carbonate and 1.758% color was added at 22.24 lb/hr. into thesecond large feed port 232. Polyisobutylene (preheated to 250° F.) wasalso added into the second large feed port at 26.1 lb/hr.

A fat mixture (225° F.) was injected into zone 240 at a total rate of14.16 lb/hr. This fat mixture included 37% hydrogenated cottonseed oil,22% hydrogenated soybean oil, 15% partially hydrogenated cottonseed oil,23% glycerol monostearate, 2.4% soy lecithin and 0.12% BHT.

Glycerin was injected into zone 260 at 3.87 lb/hr. A mixture of 85%sucrose and 15% dextrose monohydrate was added into the large feed port262 at 203.1 lb/hr. Corn syrup (100° F.) was injected into zone 260 at30.0 lb/hr. A peppermint flavor was injected at zone 260 at 3.0 lb/hr.

The zone temperature (Z1-Z5, ° F.) were set at 350, 350, 100, 55 and 55,respectively, and the screw temperature (S1) was set at 100° F. Themixture temperatures (T1-T6, ° F.) were measured at 322, 286, 161, 116,107 and 88, respectively. The screw rotation was set at 60 rpm.

The product exited the mixer at 124° F.

COMPARATIVE EXAMPLE 100% of Filler to Port 232

This comparative example illustrates the preparation of a gum base to beused to make a peppermint flavored sugar chewing gum. A blend of 48.993%dusted ground isobutylene-isoprene copolymer, 25.394% low molecularweight terpene resin and 25.613% high molecular weight terpene resin wasadded to the first large feed port 212 at 24.4 lb/hr.

A blend of 5.588% high molecular weight polyvinyl acetate, 44.690% lowmolecular weight polyvinyl acetate, 5.242% high molecular weight terpeneresin, 5.242% low molecular weight terpene resin, 37.981% fine groundcalcium carbonate and 1.258% color was added at 22.24 lb/hr. into thesecond large feed port 232. Polyisobutylene (preheated to 250° F.) wasalso added into the second large feed port at 17.7 lb/hr.

A fat mixture (225° F.) was injected into zone 240 at a total rate of14.16 lb/hr. This fat mixture included 37% hydrogenated cottonseed oil,22% hydrogenated soybean oil, 15% partially hydrogenated cottonseed oil,23% glycerol monostearate, 2.4% soy lecithin and 0.12% BHT.

Glycerin was injected into zone 260 at 3.87 lb/hr. A mixture of 85%sucrose and 15% dextrose monohydrate was added to zone 260 at 203.1lb/hr. Corn syrup (100° F.) was injected into zone 260 at 30.0 lb/hr. Apeppermint flavor was injected into zone 260 at 3.0 lb /hr.

The zone temperatures (Z1-Z5, ° F.) were set at 350, 350, 100, 55 and55, respectively, and the screw temperature (S1) was set at 100° F. Themixture temperatures (T1-T6, ° F.) were measured as 333, 292, 162, 118,110 and 90, respectively. The screw rotation was set at 60 rpm.

The product exited the mixer at 121° F.

It should be appreciated that the methods of the present invention arecapable of being incorporated in the form of a variety of embodiments,only a few of which have been illustrated and described above. Theinvention may be embodied in other forms without departing from itsspirit or essential characteristics. It will be appreciated that theaddition of some other ingredients, process steps, materials orcomponents not specifically included will have an adverse impact on thepresent invention. The best mode of the invention may therefore excludeingredients, process steps, materials or components other than thoselisted above for inclusion or use in the invention. However, thedescribed embodiments are to be considered in all respects only asillustrative and not restrictive, and the scope of the invention is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

We claim:
 1. A process for continuously producing a chewing gum basecomprising the steps of:a) continuously adding chewing gum baseingredients, including a hard elastomer, filler and one or morelubricating agents, into a continuous blade and pin mixer having aplurality of spatially separated feed inlets, at least a portion of saidhard elastomer and a portion of said filler being introduced into saidmixer through one or more first feed inlets and a portion of said fillerbeing introduced into said mixer through one or more second feed inletslocated downstream of said first feed inlets; b) subjecting the chewinggum base ingredients to continuous mixing operations within the mixer,thereby producing a chewing gum base; and c) continuously dischargingthe chewing gum base from the mixer while chewing gum base ingredientscontinue to be introduced and mixed within the mixer.
 2. A process forcontinuously producing a chewing gum base comprising the steps of:a)continuously adding chewing gum base ingredients, including a hardelastomer, filler and one or more lubricating agents, into a continuousmixer having at least one dispersive mixing zone and at least onedistributive mixing zone and a plurality of spatially separated feedinlets, at least a portion of said hard elastomer and a portion of saidfiller being introduced into said mixer through one or more feed inletslocated before the end of said dispersive mixing zone and a portion ofsaid filler being introduced into said mixer through one or more feedinlets located downstream of said dispersive mixing zone and before theend of said distributive mixing zone, the ratio of the amount of filleradded before the end of the dispersive mixing zone to the amount offiller added downstream of the dispersive mixing zone being optimized sothat the gum base contains a desired amount of filler and the dispersivemixing is effective to properly masticate the hard elastomer; b)subjecting the chewing gum base ingredients to continuous mixingoperations within the mixer, thereby producing a chewing gum base; andc) continuously discharging the chewing gum base from the mixer whilechewing gum base ingredients continue to be introduced and mixed withinthe mixer.
 3. The process of claim 2 wherein the continuous mixercomprises one piece of equipment.
 4. The process of claim 2 wherein themixer comprises a blade-and-pin mixer.
 5. The process of claim 2 whereinthe hard elastomer is brought into contact with the filler prior to anysubstantial mastication of the hard elastomer.
 6. The process of claim 2wherein the lubricating agents are introduced into the continuous mixerat two or more of said spatially separated feed inlet locations.
 7. Theprocess of claim 2 wherein the dispersive mixing zone functions as suchdue to a combination of the use of high shear mixing elements in themixer, the gum base ingredients being mixed therein, and the temperatureand fullness conditions of the mixer.
 8. The process of claim 2 whereinthe gum base is discharged from the mixer as part of a chewing gumcomposition.
 9. The process of claim 2 wherein the hard elastomer is alladded at a first feed inlet.
 10. The process of claim 2 wherein thefiller is selected from the group consisting of calcium carbonate, talc,magnesium carbonate, dicalcium phosphate and mixtures thereof.
 11. Theprocess of claim 2 wherein the lubricating agents are selected from thegroup consisting of elastomer solvents, softening agents, softelastomers, plastic polymers and mixtures thereof.
 12. The process ofclaim 11 wherein the plastic polymers comprises polyvinyl acetate. 13.The process of claim 11 wherein the elastomer solvents are selected fromthe group consisting of terpene resins, natural rosin esters andmixtures thereof.
 14. The process of claim 11 wherein the plasticizersare selected from the group consisting of fats, oils, waxes, emulsifiersand mixtures thereof.
 15. The process of claim 11 wherein the hardelastomers have a Flory molecular weight of over about 200,000 and thesoft elastomers have a Flory molecular weight of below about 100,000.16. The process of claim 15 wherein the soft elastomers are selectedfrom the group consisting of polyisobutylene, polybutadiene and mixturesthereof.
 17. The process of claim 15 wherein the hard elastomer isselected from the group consisting of isobutylene-isoprene copolymer,styrene-butadiene rubber, natural rubbers, natural gums and mixturesthereof.
 18. The process of claim 2 wherein the mixer is operated at apeak temperature greater than 175° F. in the dispersive mixing zone. 19.The process of claim 2 wherein the mixer is operated at a peaktemperature greater than 250° F. in the dispersive mixing zone.
 20. Theprocess of claim 2 wherein the mixer is operated at a peak temperaturegreater than 300° F. in the dispersive mixing zone.
 21. A method ofoptimizing a process for the continuous manufacture of chewing gum basein which chewing gum base ingredients, including a hard elastomer,filler and one or more lubricating agents, are continuously added intothe continuous mixer and mixed therein to produce a chewing gum basewhich is continuously discharged from the mixer while chewing gum baseingredients continue to be introduced and mixed within the mixer, and inwhich the continuous mixer has at least one dispersive mixing zone, atleast one distributive mixing zone downstream of said dispersive mixingzone and a plurality of spatially separated feed inlets, the methodcomprising the steps of:a) adding at least a portion of the hardelastomer, at least a portion of the lubricating agents and a portion ofthe filler through one or more feed inlets located before the end of thedispersive mixing zone; b) adding a portion of the filler through one ormore feed inlets downstream of said dispersive mixing zone and beforethe end of said distributive mixing zone; and c) optimizing the ratio ofthe amount of filler added in step a) to the amount of filler added instep b) so that the gum base produced contains a desired amount offiller and the mixing process results in an optimized texture of the gumbase.
 22. A process for continuously producing a chewing gum basecomprising the steps of:a) continuously adding chewing gum baseingredients, including a hard elastomer, filler and one or morelubricating agents, into a continuous mixer comprising a plurality ofspatially separated feed inlets, said filler being added at a pluralityof said feed inlets; b) controlling the temperature of the mixer sothat, at steady state, the peak temperature is over 250° F.; c)subjecting the chewing gum base ingredients to continuous mixingoperations within the mixer, thereby producing a chewing gum base; andd) continuously discharging the chewing gum base from the mixer whilechewing gum base ingredients continue to be introduced and mixed withinthe mixer.
 23. A process for making a chewing gum composition wherein agum base is made according to the process of claim 1 and mixed withflavoring agents and bulking and sweetening agents to make said chewinggum composition.
 24. A process for making a chewing gum compositionwherein a gum base is made according to the process of claim 2 and mixedwith flavoring agents and bulking and sweetening agents to make saidchewing gum composition.
 25. A process for making a chewing gumcomposition wherein a gum base is made according to the process of claim21 and mixed with flavoring agents and bulking and sweetening agents tomake said chewing gum composition.
 26. A process for making a chewinggum composition wherein a gum base is made according to the process ofclaim 22 and mixed with flavoring agents and bulking and sweeteningagents to make said chewing gum composition.